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<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            background-color: #F5DEB3;
        }


        body[属性样式] {
            margin-right: 50px;
            margin-left: 50px;
            margin-bottom: 50px;
            margin-top: 50px;
        }

        h1 {
            display: block;
            font-size: 2em;
            margin-block-start: 0.67em;
            margin-block-end: 0.67em;
            margin-inline-start: 0px;
            margin-inline-end: 0px;
            font-weight: bold;
        }
    </style>
</head>

<body>
    <html>

    <head>
        <meta charset="utf-8">
        <title>菜鸟教程(runoob.com)</title>
    </head>
    <body style="background-color:#F5DEB3" marginwidth="50" marginheight="50">
        <h1>这个页面显示在iframe 中</h1>
    </body>

    </html>
</body>

</html>